The Astoria Fan is a

submarine fan Abyssal fans, also known as deep-sea fans, underwater deltas, and submarine fans, are underwater geological structures associated with large-scale sediment deposition and formed by turbidity currents. They can be thought of as an underwater ve ...

. It has

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

, radiating asymmetrically southward from the mouth of the

Astoria Canyon Astoria Canyon is a submarine canyon 10 miles (16 km) offshore from the mouth of the Columbia River The Columbia River (Upper Chinook language, Upper Chinook: ' or '; Sahaptin language, Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana'' ...

. From Astoria Canyon's mouth, the fan extends about to its western end, which is the Cascadia Channel. The fan proper ends south of the canyon mouth, although its depositional basin extends southward another to the Blanco fracture zone. Astoria Fan is generally

asymmetrical Asymmetry is the absence of, or a violation of, symmetry (the property of an object being invariant to a transformation, such as reflection). Symmetry is an important property of both physical and abstract systems and it may be displayed in pre ...

. It extends roughly west of the mouth of

, and about north, to Willapa Channel. Others trace different dimensions. Headed west, the fan crosses the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

, trending sinuously down to the base of the

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

. Near Astoria Canyon, it is at a depth of . The fan is approximately long. It varies in width from to . It has numerous tributaries. The fan extends about to its western boundary, which is the Cascadia Channel. Ash from the eruption of Mount Mazama has been found, in Astoria Fan. It may have been cut in the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. It appears the Missoula Floods helped carve the fan. Astoria Fan merges into

, west of the Columbia River mouth. In the past, buried

channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Australia in Queensland and pa ...

appear to have connected the two.

Nearby submarine canyons

All of the following submarine canyons are near, headed north to south: * Clayoquot Canyon * Father Charles Canyon * Loudon Canyon * Barkely Canyon * Nitinat Canyon * Juan de Fuca Canyon * Quileute Canyon *

Quinault Canyon The Quinault Canyon is a submarine canyon, off Washington state, in Olympic Coast National Marine Sanctuary. The area It lies opposite the Quinault Reservation. From the map, it is clear the Quinault River drains into the Pacific Ocean, oppo ...

* Grays Canyon * Guide Canyon *

Willapa Canyon Willapa may refer to: * Willapa people, an Athapaskan-speaking people in Washington, United States * Willapa River, river on the Pacific coast of southwestern Washington, United States * ''General Miles'', a ship * Willapa Electric Company, an e ...

References

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Nearby submarine canyons

See also

Local geography

References

External links and references